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https://issues.apache.org/jira/browse/HAWQ-1200?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15794615#comment-15794615
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Paul Guo commented on HAWQ-1200:
--------------------------------

Just saw it. It is an interesting idea. I have two concerns, 
1) I guess Makefiles have been with proper dependencies so that non-modified 
files will not be copied, else that is a Makefile bug.
2) Actually our install script install-sh supports similar idea via the option 
"-C". The difference is that is it uses cmp.
rsync is a bit heavy for comparison since it seems that it calculates using 
hash digest and allows shift.

I just quickly hacked src/backend/Makefile.global and test install performance 
on my virtual machine,

#INSTALL = $(SHELL) $(top_srcdir)/config/install-sh -c
INSTALL    = $(SHELL) $(top_srcdir)/config/install-sh -C

No obvious improvement in my system. Actually the difference will depend on the 
cpu and io performance. Since the comparison solution will
introduce additional cpu cost for calculation and io cost for original file 
read. If write is slow (e.g. slow hard disk or through network), the solution
will be good, else no.

Anyone could easily customize it via setting the environment variable,
CUSTOM_INSTALL

> Incremental make install.
> -------------------------
>
>                 Key: HAWQ-1200
>                 URL: https://issues.apache.org/jira/browse/HAWQ-1200
>             Project: Apache HAWQ
>          Issue Type: Improvement
>          Components: Build
>            Reporter: hongwu
>            Assignee: Lei Chang
>
> Current make install process cp all copy files from source directory to 
> install prefix, this is time-consuming. We can optimize it with rsync instead 
> of cp. It could improve the development efficiency.



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